1. Field of the Invention
This invention relates to a summary content generation device and to a computer program, which generate summary content for broadcast programs in digital terrestrial broadcasting and other digital broadcasting.
Priority is claimed on Japanese Patent Application No. 2007-241371, filed Sep. 18, 2007, the content of which is incorporated herein by reference.
2. Description of the Related Art
In digital terrestrial broadcast services, subtitle information (closed-caption information) is delivered simultaneously in addition to video data. Subtitles are information used to superpose program dialogue, spoken lines, and similar onto the television images, so that, for example, even persons who are hard of hearing can enjoy broadcasts. While reproducing video data and audio data among the received digital terrestrial broadcast data, a digital terrestrial broadcast reception terminal, upon receiving subtitle data in the broadcast data, superposes the subtitle data on the reproduced video data. As digital terrestrial broadcast reception terminals, in addition to home-use television receivers, there are also terminals which employ personal computers and portable telephone sets. In particular, digital terrestrial broadcast service for portable telephone sets is called “1seg”. In this 1seg service, subtitles are always displayed, and viewing is possible without listening to audio even on trains or in other public places. Specifications for these services are stipulated by standards of ARIB (Association of Radio Industries and Businesses).
Further, among digital terrestrial broadcast reception terminals are devices comprising functions to store received broadcast data in hard disk devices or other storage media; by this means, a viewer can view a broadcast program at any time by reproducing the stored broadcast data. Hereafter, with increasing storage area capacities and falling costs, it is anticipated that it will become possible to store all the programs broadcast over one week or a longer period on a plurality of broadcast channels.
However, it is thought that, due to available time constraints, many viewers view only a portion of broadcast programs among the broadcast programs accumulated in a storage area. Moreover, while there are cases in which a single broadcast program is reproduced and viewed completely from beginning to end, there are also cases in which only a synopsis of a broadcast program is checked. When checking only a synopsis, for example, there is a method in which while fast-forwarding during reproduction, only scenes which the viewer wishes to view are reproduced normally; however, this method requires that the viewer view the fast-forwarded television images and perform operations while watching closely, requires time, and is troublesome.
Hence expectations are mounting for technology to facilitate understanding, by simple means, of the content of a single broadcast program in a short amount of time. Methods to facilitate understanding of program content include a method of extracting partial video data from the original video data to generate concatenated summary video content, and a method of extracting still images from the original video data to generate summary thumbnail content which displays a list of images. On the other hand, while there have been advances toward larger storage area capacities, the amount of data which can be accumulated is limited, and so it is desired that the data size of summary video content be as small as possible, and it is also desired that the number of images of summary thumbnail content be as small as possible.
In Patent Reference 1, a method is proposed in which measures are taken such that program content can be ascertained, and at the same time searching for a desired scene can be performed, and reproduction of video from that scene is possible. In the technology of the prior art disclosed in this Patent Reference 1, images in which subtitles are displayed are extracted from video data, and are converted into thumbnails. Then, when the viewer selects an image displayed in a list, video is reproduced from that position.
In Patent Reference 2, a method is proposed in which animation images which summarize program content are generated. In the technology of the prior art disclosed in this Patent Reference 2, images and subtitles are extracted from video, and image groups combining these are continuously switched as animation images, to generate summary content. Images used in these animation images are frame images at the time of reception of subtitles, at the time received subtitles exceed a fixed data amount, at the time a video scene changes, or at the time a fixed length of time has elapsed. Further, in order to reduce the size of summary content, image processing is performed to extract only the outlines of extracted images.    Patent Reference 1: Japanese Unexamined Patent Application, First Publication No. 7-192003    Patent Reference 2: Japanese Unexamined Patent Application, First Publication No. 2007-006308
However, in the technology of the prior art disclosed in Patent Reference 1 above, images extracted from video are merely displayed as thumbnails in a list, and as the number of images increases, the convenience of use as a list is greatly worsened. Further, in displaying a list of thumbnails, it is necessary to assume viewing using a display device with a display of a certain size, detracting from general applicability. In particular, when using portable telephone sets, which are presently in wide use, the screen size is small in order to enhance portability, and so it is difficult to view a list of thumbnails with satisfactory perceptibility.
In the technology of the prior art disclosed in Patent Reference 2, animation images which summarize the program content are generated; but as the number of images increases, the animation reproduction time grows longer, and moreover the size of the summary content data increases. Hence in order to reduce the size of the summary content data, images are converted into binary values and converted into line drawings to reduce the size of the image data itself; but as indicated by image b shown in FIG. 5 of Patent Reference 2, it is difficult to reliably ascertain the content of video from a line drawing. Further, a method to switch display of animation images with subtitle character strings superposed to images extracted from video is not disclosed. Hence when reproducing animation images, it is thought that a viewer will perform manual operations to switch and display one image at a time in sequence, but such operations are troublesome. Or, it is thought that animation images may be switched automatically at fixed intervals; but depending on the length of the subtitle character string contained in one animation image, there is the possibility that the display will be switched to the next animation image before the viewer has finished reading the subtitle character string.
Thus among methods of generating summary content for digital terrestrial broadcast programs, there is the problem of controlling the timing of switching of animation images for display, such that a viewer can understand subtitle character strings and images when generating animation content in which still images extracted from video data is also displayed, together with switching and display in order of subtitle character strings of the subtitle data. Further, it is preferable that the size of the summary content data be small, and that the reproduction time be short; but it is also important that an amount of information be provided enabling the viewer to understand the content of the original broadcast program merely by viewing the summary content. For this reason, a method of displaying highly readable subtitle character strings, while reducing the number of images used in animation content or the number of times animation images are switched, is desirable.
This invention was devised in light of the above circumstances, and has as an object the provision of a summary content generation device and computer program which enable appropriate control of the timing of switching of animation images for display, when generating animation content as summary content for digital broadcast programs.